drm/i2c: tda998x: separate connector initialisation

Separate out the connector initialisation from the rest of the drivers
initialisation.

Tested-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Jon Medhurst <tixy@linaro.org>
Acked-by: Jon Medhurst <tixy@linaro.org>
Tested-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>